Big noteEdit 2:
Okay, after more testing, it seems like the bug is serious after all. Deleting several backups manually causes DISE to delete everything and then crash. Please just jump down to --- End of big note ---.

Edit:
I wrote the big note as quickly as I could, without testing this properly first. After giving it a little more testing, it seems like the bug isn't as serious as I thought. After trying it again, it didn't delete all of my backups, nor did it crash after deleting a a few backups. However, it did crash after I deleted all of my backups manually and then chose Yes. If you give this some testing, please let me know how serious it is.

Actually, I couldn't understand why DISE would delete all of the backups, so maybe I simply deleted them all earlier either intentionally or accidentally, and chose Yes. My short term memory can sometimes be, well, short!┐('～`；)┌--- End of big note ---

I found a serious bug, but it's easy to avoid. If your backup limit is reached, don't choose Yes to overwrite your oldest backups if you already deleted some manually! It will cause DISE to delete all of your backups and then crash! If you deleted your backups manually, choose No.